This study is an effort to develop an efficient process for low-cost production of calcium-l-lactate (CaL 2 ). CaL 2 showed higher inhibitory effect on lactate production than ammonium-l-lactate (NH 4 ) at lactate concentration lower than 100g/L, but it showed lower inhibitory effect at higher lactate concentration. The strain Lactobacillus rhamnosus (NBRC 3863) was resistant to glucose inhibition and final CaL 2 concentration increased with initial glucose concentration increasing up to 190g/L. High-concentration CaL 2 induced, however, flocculation of fermentation broth, causing incomplete fermentation. It was confirmed that stirring speed markedly influenced flocculation, an increase of the stirring speed leading to an earlier flocculation. Formation of colloidal CaL 2 during fermentation was considered to be the cause of flocculation in this study. Addition of YE raised fermentation efficiency and made complete fermentation feasible. In the fermentation with 25g/L YE, glucose was completely consumed and final CaL 2 concentration of 220g/L was obtained, when flocculation did not yet occur. In this study, CaL 2 crystals and activated carbon powder were added as nucleation sites to get earlier crystallization of colloids and to decrease the inhibitory effect of CaL 2 , and so to increase productivity. Of the two nucleation sites, activated carbon powder showed higher performance in CaL 2 production. Finally, the feasibility of crystallization-based recovery without concentration step was discussed.